The present invention relates to a driving mechanism for pneumatic tools and rotor rotatably contacts the inside of the casing at two surfaces and one point so that the rotor can be operated by large torque.
A conventional driving mechanism for pneumatic tools is shown in FIGS. 1 to 3 and generally includes a casing 10 having a front hole 12 in a front surface of the casing 10 and a rear hole 13 in a rear surface of the casing 10. A rotor 20 is rotatably received in the casing 10 and has two grooves 23 and 24 respectively defined in two opposite outside of the rotor 20. A hole 21 is defined in the rotor 20 and two driving surfaces 22 extend inward from an inside of the hole 21. Two rods 18 extend through the front surface of the casing 10 and are respectively engaged with the two grooves 23, 24 so as to connect the rotor 20 to the casing 10. A shaft 30 extends through the front hole 12 of the casing 10 and the hole 21 in the rotor 20. A front end of the shaft 30 has an engaging member 34 to be connected with a socket (not shown) and a rear end 32 of the shaft 30 is engaged with the rear hole 13. The casing 10 further has a toothed driving part 14 so as to be connected to a driving source. A block 33 extends from the shaft 30 and is located in the hole 21 of the rotor 20. A flange 31 is engaged with the inside of front surface so that the shaft 30 will not drop from the front hole 12. Referring to FIGS. 4 and 5, when the casing 10 is rotated, the rotor 20 is rotated together with the casing 10 and the block 33 will be pushed by the driving surface 22 so as to output a torque.
Referring to FIG. 6, when the object to be tightened is locked, the shaft 30 cannot be rotated any further, the rotor 20 is forced to roll on one of the rods 18 a small angle to disengage the driving surface 22 from the block 33. The rotor 20 keeps on rotating and the point xe2x80x9cAxe2x80x9d contacts the block 33 and pushes the rotor 20 to roll on the rod 18 to its operation position again. Therefore, the driving surface 22 can impact the block 33 again. If the user feels two or three times of the shifting of the rotor 20, he/she knows that the object is totally tightened.
FIG. 9 shows that two rotors 20 are installed in the casing 10 and the shaft 30 has two blocks 33 so that the shaft 30 can be operated in balance.
The torque output is decided by the engagement between the two rods 18 and the two grooves 23, 24. The rods 18 could be worn out to affect the torque and the block 33 is driven by only one driving surface 22 may cause shaking.
In accordance with one aspect of the present invention, there is provided a driving mechanism for pneumatic tools and the mechanism comprises a casing having a groove defined in an inner periphery of the casing and two support surfaces extend from the inner periphery of the casing. A rotor is received in the casing and has a passage defined therethrough. A ridge extends from an outer periphery of the rotor and is engaged with the groove of the casing. A surface is defined in an outer periphery of the rotor and engaged with the two support surface. Two driving surfaces are defined in an inner periphery of the rotor. A shaft extends through the passage of the rotor and has a protrusion extending from an outer periphery of the shaft. The protrusion is driven by one of the two driving surfaces.
The primary object of the present invention is to provide a driving mechanism for a pneumatic tool wherein the shaft is driven by two driving surfaces.
The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention.